Method and system for processing mass analysis data

Abstract

In an imaging mass analysis, image information of a sample allows users to grasp specific information about the sample, such as distribution of a portion with a particular function or effect. The mass spectrum intensity data are normalized for each pixel so that the sum of the intensities over the entire mass-to-charge ratio (m/z) is one. Entropy is calculated by totaling the product of the intensity normalizing at each m/z and the logarithm of that intensity over the entire m/z range. After the entropy is calculated for each pixel, the pixels are colored according to their entropy values to display a two-dimensional color image of entropy distribution. The entropy of a cancerous portion is relatively small because of a high content of a specific kind of substance and the simplified composition of the substances. Thus, the cancerous part and the normal part of the entropy image can be distinguished.

The invention claimed is: 
     
       1. A mass analysis data processing method for processing data collected by performing a mass analysis for each of a plurality of micro areas set in a two-dimensional area on a sample, comprising the steps of:
 a) normalizing, for each of the micro areas, intensity information of mass spectrum data corresponding to the micro area; 
 b) calculating entropy at each micro area based on the mass spectrum data after normalization; and 
 c) coloring the micro areas by giving each micro area a display color corresponding to the entropy calculated at each micro area, for creating a colored two-dimensional mass analysis image corresponding to the aforementioned two-dimensional area, and for displaying the created image. 
 
     
     
       2. A mass analysis data processing system for processing data collected by performing a mass analysis for each of a plurality of micro areas set in a two-dimensional area on a sample, comprising:
 a) a normalizing processor for normalizing, for each of the micro areas, intensity information of mass spectrum data corresponding to the micro area; 
 b) an entropy calculator for calculating entropy at each micro area based on the mass spectrum data after normalization; and 
 c) a display information creator for coloring the micro areas by giving each micro area a display color corresponding to the entropy calculated at each micro area, for creating a colored two-dimensional mass analysis image corresponding to the aforementioned two-dimensional area, and for displaying the created image on a display screen. 
 
     
     
       3. The mass analysis data processing system according to  claim 2 , wherein the entropy calculator calculates the entropy by adding a product of an intensity value at each mass-to-charge ratio and either a natural or common logarithm of that intensity value in a mass spectrum over an entire range of the mass-to-charge ratios. 
     
     
       4. The mass analysis data processing system according to  claim 2 , wherein the normalizing processor performs the normalization in such a manner that intensity information of the mass spectrum data is weighted according to the mass-to-charge ratio. 
     
     
       5. The mass analysis data processing system according to  claim 2 , wherein:
 a reference selector for selecting one of the micro areas as a reference of comparison is further provided; and 
 the entropy calculator calculates relative entropy of each micro area with reference to the entropy of a micro area selected as the reference of comparison by the reference selector. 
 
     
     
       6. The mass analysis data processing system according to  claim 2 , further comprising a binning processor for performing, before the normalization by the normalizing processor, a binning process in which the mass spectrum data of a plurality of micro areas adjacent to or neighboring with each other within the two-dimensional area are added or averaged.